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.TH CURLOPT_HSTS_CTRL 3 "4 Sep 2020" "libcurl 7.74.0" "curl_easy_setopt options"
.SH NAME
CURLOPT_HSTS_CTRL \- control HSTS behavior
.SH SYNOPSIS
.nf
#include <curl/curl.h>

#define CURLHSTS_ENABLE       (1<<0)
#define CURLHSTS_READONLYFILE (1<<1)

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_HSTS_CTRL, long bitmask);
.fi
.SH EXPERIMENTAL
Warning: this feature is early code and is marked as experimental. It can only
be enabled by explicitly telling configure with \fB--enable-hsts\fP. You are
advised to not ship this in production before the experimental label is
removed.
.SH DESCRIPTION
HSTS (HTTP Strict Transport Security) means that an HTTPS server can instruct
the client to not contact it again over clear-text HTTP for a certain period
into the future. libcurl will then automatically redirect HTTP attempts to
such hosts to instead use HTTPS. This is done by libcurl retaining this
knowledge in an in-memory cache.

Populate the long \fIbitmask\fP with the correct set of features to instruct
libcurl how to handle HSTS for the transfers using this handle.
.SH BITS
.IP "CURLHSTS_ENABLE"
Enable the in-memory HSTS cache for this handle.
.IP "CURLHSTS_READONLYFILE"
Make the HSTS file (if specified) read-only - makes libcurl not save the cache
to the file when closing the handle.
.SH DEFAULT
0. HSTS is disabled by default.
.SH PROTOCOLS
HTTPS and HTTP
.SH EXAMPLE
.nf
CURL *curl = curl_easy_init();
if(curl) {
  curl_easy_setopt(curl, CURLOPT_HSTS_CTRL, CURLHSTS_ENABLE);
  curl_easy_perform(curl);
}
.fi
.SH AVAILABILITY
Added in 7.74.0
.SH RETURN VALUE
Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.
.SH "SEE ALSO"
.BR CURLOPT_HSTS "(3), " CURLOPT_CONNECT_TO "(3), " CURLOPT_RESOLVE "(3), "
.BR CURLOPT_ALTSVC "(3), "
